Volcán Parinacota is the southernmost and youngest of a pair of volcanoes forming the Nevados de Payachata volcanic group along the Chile-Bolivia border. The symmetrical, 6348-m-high Parinacota volcano forms a twin volcano with the dominantly Pleistocene, 6222-m-high Pomerape volcano, which towers above a low saddle to the NE. Collapse of Parinacota about 8000 years ago produced a 6 cu km debris avalanche that traveled 22 km to the west and blocked drainages, forming Lake Chungará. Holocene eruptive activity has subsequently reconstructed the Parinacota stratovolcano, which contains a pristine, 300-m-wide summit crater and youthful lava flows on the western flanks. Although no historical eruptions are known from Parinacota, Helium surface-exposure dates have been obtained for eruptions during the past two thousand years both from the main cone and the Ajata group of satellite cones and lava flows on the south and SW flanks.